Effects and mechanisms of grain refinement in aluminium alloys

Abstract

Grain refinement plays a crucial role in improving characteristics and properties of cast and wrought aluminium alloys. Generally Al-Ti and Al-Ti-B master alloys are added to the aluminium alloys to grain refine the solidified product. The mechanism of grain refinement is of considerable controversy in the scientific literature. The nucleant effects i.e. which particle and its characteristics nucleate α α-Al, has been the subject of intensive research. Lately the solute effect i.e. the effect of dissolved titanium on grain refinement, has come into forefront of grain refinement research. The present paper attempts to review the literature on the nucleant effects and solute effects on grain refinement and addresses the importance of dissolved titanium in promoting nucleation of α α-Al on nucleant particles.

Potential of an Al-Ti-MgAl2O4 Master Alloy and Ultrasonic Cavitation in the Grain Refinement of a Cast Aluminum Alloy

“…To confirm the cavitation-induced fragmentation of Al 3 Ti, 100 g of master alloy was remelted at 1173 K (900°C) and cast without ultrasonication. Large Al 3 Ti needles over 200 lm in size were formed in the master alloy (Figure 7). B.…”

“…[1][2][3][4][5] From the various grain refinement techniques, the most common practice is the addition of specialized master alloys containing potent nucleation substrates (TiB 2 , TiC, AlB 2 ), primary intermetallics (Al 3 Ti, Al 3 Nb, etc. ), and/or growth-restricting alloying elements (Ti, V, Nb, etc.).…”

“…[6][7][8][9][10] In current industrial practice, Al-Ti-B (Al-Ti-TiB 2 ) and Al-Ti-C (Al-Ti-TiC) master alloys are the most common grain refiners used in cast and wrought Al alloys. [2,3] The grain refinement mechanisms as well as some technological issues related to Si or Zr poisoning of Al-Ti-B grain refiners are thoroughly scrutinized by theoretical models and experiments. [11,12] Despite the commercial success of Al-Ti-B and Al-Ti-C grain refiners, some drawbacks are related to their application such as reduced performance in high-Sior Zr-containing alloys and agglomeration of borides in Al-Ti-B master alloys and a narrow process-parameter window for Al-Ti-C master alloys.…”

Corrosion Characterisation of Al-Cu Reinforced In-Situ TiB2

“…This behavior can be attributed to the positive influence of TiB 2 addition on the grain size refinement. The fine grained materials have a more advantageous behavior with respect to corrosion and oxidation have been approved [8]. From Figure 3 above, Al-6wt.%Cu alloy with 3wt.%TiB 2 showed the best corrosion resistance compare to other composition of TiB2.…”

Effect of Titanium and Boron on the Stability of Grain Refinement of Al-Cu Alloy

“…That is why the so-called grain refiner and inoculants differ from microalloying, the effects of which are independent of time [11][12]. Literature provides limited data [11][12][13][14] on the primary structure -maximum undercooling relationship in the Al-5Cu system as a function of time (fading effects) lapsed from the grain refinement treatment. The purpose of this study was to investigate the effect of stability in modifying the primary structure -dendrites of α(Al) phase in the aluminum-copper type of alloys, using selected master alloys (1) Al-5%Ti-1%B, (2) Al-5%Ti and (3) Al-3%B as well as examining Brought to you by | MIT Libraries Authenticated Download Date | 5/11/18 7:08 AM the effect of the initial titanium content in the base alloy on the stability of these effects.…”